The invention relates to compressor apparatus for the production of compressed gas, especially for a pneumatic brake installation.
A type of compressor apparatus is described in connection with a pneumatic brake in German Patent Application P 31 36 948.0, published in Germany on Mar. 31, 1983. In this apparatus, a pressure regulation apparatus, a so called governor which is responsive to the pressure within the reservoir is used, among other things, to switch over the compression phase of the air compressor operation into an idle phase. The pressure regulation valve apparatus, connected between the reservoir and the suction portion of the compressor, when a predetermined reservoir pressure is surpassed, switches so that a piston located in the cylinder head of the compressor is acted upon by compressed air. The stroke movement of this piston which is thereby triggered pushes open the suction valve of the compressor by means of a piston tappet. As a result of this open connection made between the suction chamber and the compression chamber of the compressor, the latter conveys no compressed air during the idle phase. This continues until there is a predetermined drop in the reservoir pressure, when the pressure regulation valve apparatus reverses and the piston returns to its initial position as a result of the cessation of pressurization, so that the suction valve in the transport phase can once again exercise its normal function.
It is also known that, in compressors, the use of plate valves is more advantageous than the common use of disc valves, since with the same valve clearance volume, the plate valves make available a greater admission cross section than the disc valves. The advantages of a larger admission cross section include lower suction losses and a greater efficiency of the compressor. The use of suction valves of the preferable plate valve design presents no problems at all, if the compressor is so arranged that the reservoir pressure is regulated by means of a valve apparatus in which, in a known manner, a pressure which surpasses a predetermined pressure level is exhausted into the atmosphere. In other words, the compressor continues to produce compressed air in the idle phase so that the suction valve retains its normal function during this phase.
A phate valve which opens during the suction process of the compressor has its plate projecting into the compression chamber and, during the compression process, is again pushed out of the compression chamber and out of the piston stroke area of the piston, onto its valve seat in the closed position. In the normal compression phase and during an idle phase of the compressor in which the excess pressure is vented into the atmosphere, a plate-type suction valve creates no problems. However, when the pressure is regulated by means of a governor and the suction valve is held open during the idle phase, measures must be taken which prevent the piston, when moving upward, from striking the valve plate which projects into the compression chamber. That is, the space above the piston, in its topmost stroke position, must exhibit a correspondingly greater height. The consequence of this is a significant decrease in efficiency, an elongated design of the compressor, and longer filling times for the apparatus. For this reason, the lesser of two evils has been accepted and the suction valves are designed as disc valves.
The object of the invention, therefore, is the creation of compressor apparatus of the type described in which, in spite of pressure regulation by means of a governor, the suction valve of the compressor can be designed as a plate valve.